I believe salts are used to harden water, not soften it. A lot of city-supplied water in these parts is softened so people add salts to get a more authentic water profile (at least for certain styles). People on well water probably have plenty hard water.

I add a teaspoon or two, although admittedly I've never done a side-by-side comparison of beer with and without.

but there are many kinds of 'salt'. water softeners work by replacing the calcium and magnesium ions in hard water with sodium ions. Sodium doesn't cause the hard scales to form like calcium/magnesium does. So, it replaces alkaline metals with just alkali metals.

To preface:
Japan LOVEs it's water, I cannot even try to over emfasise Japan's water fetish. It comes from sake brewing and the temples' claims of water cleanliness. My area is famous for its "miyamizu" (literally: temple/ holy water) used for beer and sake brewing.

My Real questions are A and B;
A Why
B How

Why is the water chem so important? I am currently doing a pretty simple steeped grains with extract brew. Really the water chem should only effect the steep if anything.

How can I check my water's make up? Hardness and alkainity aren't really tastible, are they. Is it worth checking for the extract(with grain/ partial mash) homebrewer?

Sorry to ask questions in someone else's thread, I hope we can all learn a bit.

Well, as anybody with well water can tell you, hard vs soft certainly affects the flavor of the water, which will therefore effect the flavor of the beer to some extent. Water makeup also affects its pH which therefore affects extraction from the grains. I imagine that molecules of various substances in the water also interact during the mash/boil/fermentation in some way, but that's beyond me.

you can call your local water athority and find out all the spec's on your water, including bacteria count. every water plant has a test lab that tests the water, if your curious, just give em a call, tell em what your doin and they should have no problems answering any questions you might have!!